FLUCTUATIONS OF TOTAL ANTIOXIDANT CAPACITY (TAC) IN FRESH AND REFRIGERATED FRUIT JUICES BOUGHT IN BENIN CITY, NIGERIA

Abstract

Fruit juices contain phenolic compounds and vitamin C which possess antioxidant capacity. A knowledge of the effect of refrigerated storage on the total antioxidant characteristics of citrus fruits is necessary. Total antioxidant capacities (TAC) of nine Nigerian fruits were collected from a local market. The pulp and seed free juices were obtained using a Gallenkamp juicer. The fresh fruit juices namely; Green Apple, carrot, Grape, Mango (Mangifera indica), ?Bush mango‘(Irvinga gabonesis), Orange, pawpaw, pineapple and watermelon were stored in plastic containers and refrigerated at 20C for 0, 15, 30,60,120, 240,and 360minutes. The juices were thereafter assayed for total antioxidant capacity during the timed intervals. Fresh Mango fruit juice had the highest TAC with a value of 76.62 ± 0.16mM Trolox Equil/L. Pawpaw and pineapple juices had the lowest value of 11.89±1.29 mM and 12.91± 1.05mM Trolox Equil/L respectively. The results showed general fluctuations in the TAC of all the fruit juices. These values fluctuated between 15 and 30minutes period and rose to a peak between thirty minutes to two hours, except for apple which peaked at the fourth hour. Thereafter a downward trend was observed in all the fruit juices. TAC decreased thereafter to values lower than that obtained at 0hr. There were no significant difference at p ? 0.05 between the values for TAC at 0 and 6hr for carrot, grape, apple and pineapple juices. Therefore these juices have the greatest storage stability and the smallest antioxidant capacity decrease. Watermelon and pawpaw juices have the lowest TAC and after 6hours of refrigerated storage, the values were significantly lowered. Fruit juices should be consumed within two hours of its preparation to benefit maximally from its antioxidant content and effect